Reactivity-promoting criterion based on internal vibrational energy redistribution
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Communicated by Joshua Jortner, Tel Aviv University, Tel Aviv, Israel, May 2, 2007 (received for review December 21, 2006)
Abstract
We propose to introduce intrinsic dynamical properties as a criterion for promoting reactivity of small size noble metal reactive centers relevant for heterogeneous catalysis. To illustrate the concept, collisions between Ag6 − or Au6 − clusters and molecular oxygen have been investigated with direct ab initio molecular dynamics by using DFT. We show that different nature and efficiency of internal vibrational energy redistribution (IVR) during reaction dynamics is responsible for significantly different sticking probabilities of O2 to gold and to silver clusters. In the case of Au6 − and O2 collisions, resonant IVR occurs between two subunits activating O2 and promoting subsequent oxidation reactions. In contrast, a dissipative IVR in Ag6 − and O2 molecule prevents O2 to react with other adsorbates. These findings allow us to introduce the nature of IVR as a criterion for promoting the reactivity of noble metal clusters: Resonant IVR between reactants promotes reactivity toward adsorbates.
Footnotes
- *To whom correspondence should be addressed. E-mail: vbk{at}chemie.hu-berlin.de
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Author contributions: R.M. and V.B.-K. designed research; R.M., C.B., and V.B.-K. performed research; R.M., C.B., and V.B.-K. analyzed data; and R.M., C.B., and V.B.-K. wrote the paper.
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The authors declare no conflict of interest.
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↵ † The “cluster plane” is defined by the three inner atoms of the noble metal cluster. Deviation from planarity expresses the distance of the outer atoms with respect to the plane.
- Abbreviations:
- DFT,
- density functional theory;
- DOS,
- density of states;
- IVR,
- internal vibrational energy redistribution;
- MD,
- molecular dynamics.
- © 2007 by The National Academy of Sciences of the USA
